1. Field of the Invention
The invention herein pertains to the field of bicyclothiadiazinones and processes for their preparation.
2. Description of the Prior Art
Thiadiazinone dioxides as a class are known compounds. Unsubstituted or substituted benzo- and pyridothiadiazinone dioxides have been disclosed in the art.
Exemplary processes for preparing the above compounds include cyclizing the corresponding o-sulfamidobenzoic acids in the presence of phosgene and a basic catalyst (U.S. Pat. No. 3,822,257) or cyclizing the corresponding pyridinecarboxylate with a condensing agent such as phosphorus oxychloride, thionyl chloride or aqueous or alcoholic alkaline solutions, e.g., methanol, sodium methylate, aqueous sodium hydroxide or the like (U.S. Pat. Nos. 3,920,641 and 3,989,507). The same condensing agents have also been used to cyclize N-alkyl-N'-o-carboxyphenyl sulfamides or N-alkyl-N'-o-carboalkoxyphenyl sulfamides (U.S. Pat. No. 3,708,277) or other sulphaamido carboxylic acid derivatives (U.S. Pat. No. 3,940.389).
Still another method of preparing certain of the above compounds is to cyclize the corresponding N-acyl sulphamides in the presence of acid-binding agents such as alkali carbonates or alcoholates or tertiary organic bases (U.S. Pat. No. 3,041,336).
It has been found that in some cases cyclizations proceed in poor yields in basic media when bulky substituents, e.g., branched chain alkyl groups, are present on the N' atom of the intermediate sulphamido compound.
Accordingly, it is an object of this invention to provide a process for preparing the title compounds which proceeds smoothly without regard to the nature of the N' substituent, i.e., whether in the case of alkyl substituents they are linear or branched chain in configuration.